Contourite drift evolution and related coral growth in the eastern Gulf of Mexico and its gateways

Abstract

Sediment subbottom profiler and multi-beam data reveal that sediment drifts evolved in various depth intervals between 420 and 650 m water depth in the eastern Golf of Mexico and its gateways. Drift evolution on the western flank of the Yucatan Strait is controlled by the northbound Loop Current down to 800 m and by a countercurrent beneath. On the northern Campeche Bank and the West Florida Slope, drifts evolved in depth of 520-600 m and 420-550 m, respectively. In both instances, the causative contour current represents a counter flow to the Loop Current. The varying depth ranges correlate with an eastward rise of the upper boundary of the Antarctic Intermediate Water. The geometry and reflection pattern of upper slope deposits strongly suggest that the causative bottom current velocities in the eastern Gulf of Mexico varied significantly in space and time. The subbottom profiler data further show peculiar stacked diffraction hyperbolae in depths between 480 and 600 m. Camera and video observations from the seafloor off western Florida imply that the diffraction hyperbolas are formed by boulders and cliffs of sedimentary rock, which are locally colonized by coldwater corals, such as Lophelia pertusa, octocorals and stylasterids.

Environmental forcing of the Campeche cold-water coral province, southern Gulf of Mexico

“…The western part of the map shows an extensive more or less plain area at ∼ 440 m water depth. A NNW-SSE orientated and ∼ 40 m-high escarpment separates this rather shallow and plain area from a gently dipping slope to the east, which covers the water depths between 480 and 600 m. Further downslope below ∼ 600 m water depth, the slope is followed by a more gently dipping area which comprises smooth sediment of a major drift sediment body (Hübscher et al, 2010). The first 3-5 km of the dipping slope east of the edge are covered by linear and steep-sided elongated mounds between 500 and 600 m water depth.…”

“…Both the mounds and the sediment drift overlay a regional truncation surface ( Fig. 2b; Hübscher et al, 2010). The mounds have average heights between 20 and 40 m but can even reach heights of up to 50 m. They vary in length from a few tens of meters to > 1000 m, and trend in two directions.…”

“…This finding was unexpected as available data from a few dredge haul stations only described the occurrence of the scleractinian CWC Madrepora oculata along the margin of the Campeche Bank, north of the Mexican Yucatan Peninsula (Cairns, 1979;Schroeder et al, 2005). Only in 2010 was more detailed information provided, when hydroacoustic surveys revealed "mound-like" structures between 500 and 600 m water depth along the margin of the bank (Hübscher et al, 2010). Without any groundtruthing being available at D. Hebbeln et al: Environmental forcing of the Campeche cold-water coral province 1801 that time, it only has been speculated that these structures might be CWC mounds (Hübscher et al, 2010).…”

“…Further west in the Gulf of Mexico, L. pertusa appears to be more scattered, forming isolated mound-like structures along the west Florida slope (Newton et al, 1987;Hübscher et al, 2010) and in the northern Gulf of Mexico (Moore and Bullis, 1960;Schroeder, 2002;Reed et al, 2006;Cordes et al, 2008;Becker et al, 2009;Davies et al, 2010). Summarizing the current knowledge, Mienis et al (2012) conclude that within the Gulf of Mexico CWC mound structures have been rarely found, except on the west Florida slope and in the Viosca Knoll area (Fig.…”

“…Only in 2010 was more detailed information provided, when hydroacoustic surveys revealed "mound-like" structures between 500 and 600 m water depth along the margin of the bank (Hübscher et al, 2010). Without any groundtruthing being available at D. Hebbeln et al: Environmental forcing of the Campeche cold-water coral province 1801 that time, it only has been speculated that these structures might be CWC mounds (Hübscher et al, 2010).…”